I don't think I saw this build before. Very cool. And the funny thing is that I'm not normally a huge fan of diesel conversions.

But this one is different. Cool fab skills. AND I have spent hundreds of hours next to a 4-53 just like this one in the engine lab. I love the scream of these beasts. I see the pics and I can almost hear it. And smell it.

I don't think I saw this build before. Very cool. And the funny thing is that I'm not normally a huge fan of diesel conversions.

But this one is different. Cool fab skills. AND I have spent hundreds of hours next to a 4-53 just like this one in the engine lab. I love the scream of these beasts. I see the pics and I can almost hear it. And smell it.

Nice work!

Thanks for the complement. We share a love of the sounds that Detroit Diesels make.

I haven't made much progress lately. We have a short summer here (the aspen leaves are already turning) so I spend my summers working outside.

I'm currently focusing on completing the underhood - the air filtration, A/C and electrical systems.

Summer is over, the chain saw and wood splitter are put up for the winter and the plow is on the Mog. Time to get back to work on the old GMC.

I restored/modified the A/C unit for the truck. I decided to do it now because of my paranoia from the air cleaner housing debacle. I want to make sure that I know where the all parts will be when I finally come up with an air filter design.

Even though I purchased the truck in an area where good A/C is important (St. George, UT), I knew that there were issues. The brass gate valve in the heater hose was the first clue:

In the 5 years that I drove the truck before I started this project, the A/C performance was disappointing. I checked the pressures and they were good - so there was plenty of Freon and the compressor worked fine.

After I disassembled the A/C unit, I found that the warm/cold air damper was binding on both sides so it would not seal in either heat mode or cool mode. In fact, the gap on either side at full travel was more than an inch. No wonder, the A/C didn't work satisfactorily. The only good news is that the heater puts out so much heat that it was able to overcome the cold air coming through the evaporator (at 9000' elevation, heat is much more important than A/C). A little trimming of the damper gaskets solved the problem. Now it snuggles into the gasket on both sides and seals well.

I also decided to convert from the continuous running POA style control to the cycling compressor control. This meant a new evaporator and accumulator had to be installed. I will modify the wiring later when I complete the engine compartment harness.

Here's what it looks like all cleaned up and sitting in the truck:

Now that I have both ends fixed, I can start working on the tubing and hoses for the refrigerant.

Every used vehicle that I have purchased has included some electrical modification(s) by the previous owner(s). Every one of the modifications have been dangerous in some way. For one, none of the modifications have included proper circuit protection. Most have included lamp cord - not the best for automotive wiring, few have included any protection from chafing, etc. It has all been bad.

My '72 was no exception. The only difference was that the previous owner(s) were good at hiding their sins. I didn't find the poor wiring until I took the truck apart. Then, I couldn't believe that I had driven it for 5 years without having a fire. I'm happy to be lucky...

I'm adding a few circuits of my own and intend to do the job right. I need both new circuits and relays to control some substantial loads - trailer wiring, vacuum pump and air compressor. I started with a Painless Wiring Cirkit Boss and a Hella Relay Panel.

The Cirkit Boss has 4 circuits powered from a relay that operates from the ignition key and 3 always hot circuits. I have used one on my daily driver for 15 years and it has performed flawlessly.

Since the wires come out the bottom of both the Cirkit Boss and the relay panel, I fabricated a mounting bracket for the to mount to the driver's side inner fender. Here it is on the workbench:

Here it is mocked up in the pickup from the front:

Here it is from the side:

A couple of coats of black paint and it will be ready to go.

Since the hoses for the hydroboost and power steering arrived from Summit Racing, I decided to mock them up as well:

I'm making progress on the underhood equipment, I still have a ways to go...

Very nice work! Did you make the hoses or do they offer a kit for them? Those fittings for the hydraboost and pump weren't cheap when I got mine.

Unfortunately, they do not offer a kit. I had to order the hose and fittings seperately. They are still not cheap; but, the cost was comparable to the prices that I have paid for other hydraulic hoses. The fittings are reusable so I cut and assembled the hoses myself. At least it saved me a trip to town to have them crimped.

Such an awesome build. Love the 2-strokes. I still see a lot of them in generators. I have even serviced some rare ones like 3 qty 24v71's and 2 qty 12v149's. Most of them are 6v92's or 6-71's though. Is there any new progress?

Such an awesome build. Love the 2-strokes. I still see a lot of them in generators. I have even serviced some rare ones like 3 qty 24v71's and 2 qty 12v149's. Most of them are 6v92's or 6-71's though. Is there any new progress?

Thanks for the compliment. Most of the 2 cycle Detroits that I have seen have been on generators and fire water pumps. Tha largest that I have seen and heard was a 16V-149 on a generator.

I'm still working on the underhood stuff - A/C and batteries. I had to mount the A/C compressor on the driver's side of the engine because the alternator and water pump were on the passenger's side. I didn't want to route the A/C hoses over the top of the engine which created a new set of problems - more modifications to the core support, long lengths of A/C tubing, new brackets, etc. It has been slow going, lots of time and not a lot to show for it...

I finally finished the mock-up of the A/C hoses and tubing. I had to mount the A/C compressor on the driver's side because the water pump, and consequently the alternator, were on the passenger side. On Detroit Diesels, the water pump is on the side and driven off of the camshaft or balance shaft by a couple of v-belts. The alternator is used to adjust the tension of the v-belts.

Mounting the compressor on the driver's side created a problem - how to route the hoses. I considered going over the top of the valve cover; but, didn't like that option. I decided to go around the front.

Here's a photo of the driver's side showing the compressor and hoses:

Here's a photo from the front showing the condenser and the tubing:

Here's a couple of photos on the passenger side showing the evaporator and the hoses:

I still need to take the hoses to town to have the ends crimped on. Once I get that done, I'll be able to pull the system down and see if there are any leaks.

With the new year, I thought that it was time to change gears (literally). My brother and my two sons were out for New Year's and I was inspired by the thought of having help to move the parts for this heavy (350+ lbs.) transmission.

The transmission is an Eaton Fuller RT-6610. I have 4 tasks for this overhaul:

1. Replace/refurbish - replace all the bearings and the output shaft seal (the only seal) to ensure the longevity of the transmission.

2. Convert to overdrive - the difference between a RT (direct drive) and a RTO (overdrive) transmission is the input gear, 4/9 gear and the position of the first two gears on the countershafts. I purchased an overdrive kit for the transmission that included new input and 4/9 (now 5/10 - overdrive) gears, a new shift fork and new sliding clutch.

3. Installation of studs for the transmission rear support - although the transmission is perfectly happy cantilevered off of the bell housing, I want to install a rear support for it. The transmission weighs 350lbs. and the engine weighs 1100 lbs. so the rear engine mounts have roughly 900 lbs. on them when the transmission is cantilevered. I don't like putting that much weight on a single point of the chassis. The transmission arrived with plugs in the holes for the studs. The plugs have, so far, resisted all my attempts to remove them. I will probably end up drilling them out.

4. Cleaning and painting - the exterior of the transmission is very rusty. I will remove the rust and paint it.

Here's a shot of the beast on the operating table:

Here's a shot of the two sections apart. It took us hours to get them apart, even though the transmission has jacking bolts to speed the process, because the alignment dowels were rusted to the case.

The left side countershaft did not come out easily either. The rear bearing was on the shaft so tightly that I could not drive it off. I had to carefully cut it out of the transmission. Here's what was left after I got it and the shaft out:

All my help has gone home; but, we were able to complete the disassembly and press the gears off and back on the counter shafts (the difficult jobs). I'm left with the cleaning, painting and re-assembly. That will be the next post(s).

The transmission is back together. All I need to do now is finish painting it and put it back into the truck. It is now an RTO-6610. Have a look at the photos below and see if you can tell the difference.

Before:

After:

See the photo below for an explanation of the difference.

The gears with the red arrows are swapped for the ones with the green arrows & vice-versa and the gears with the blue arrows are replaced.

This modification converts what was 4/9 (right & up) to 5/10. See the diagram below for the change in the shift pattern:

Every time that I complete an overhaul, I learn something. Here's what I learned from this overhaul:

1. RTFM (I already knew this one; but, it's worth repeating) - Fuller has wonderful manuals on-line and they are free. The manual for this transmission is the most complete that I have ever seen.

2. Take lots of photos and bag & tag the parts (I knew this one too).

3. Expect to replace the synchronizers. There are synchronizers for the air shifted auxiliary section. New synchronizers were not included in the overhaul kit. The ones in my transmission were trashed. I had to wait a week for them to be delivered once I found that they were bad.

4. Assemble the synchronizers in a tub. The synchronizers have 3 very strong springs. To assemble them around the sliding clutch, they must be compressed. If you get the synchronizers slightly cocked, one of the springs will shoot out. In my case, it went 15 feet and rolled under something too heavy to move, leaving me laying on the floor with a magnet to retrieve it.

5. When installing the countershafts into the auxiliary section, slide the shafts in first, align the timing marks and then start the bearings. The instructions say to start the bearings into their registers first; but, I could not see the timing marks on the teeth with the bearings started. By sliding the shafts in first, I could see the marks through the registers.

Once I have re-installed it, I will start working on the rear support.

Very nice! I have had to chase down a few of those springs before too. Haha

It's been a lifelong struggle for me. After 50 years of working on vehicles (as a hobby), I've finally gotten to the point that I do something after I launch the spring for the first time. At this rate, I won't live long enough to actually anticipate the spring flying out before it occurs; but, I'm delighted that I'm making progress...

There are some other players making the billet hinges now. I've been watching these but haven't justified them yet. I haven't researched any reviews on these but the price seems fair and the hinges look nicely made.

There are some other players making the billet hinges now. I've been watching these but haven't justified them yet. I haven't researched any reviews on these but the price seems fair and the hinges look nicely made.

I re-installed the transmission. Installing a transmission from above into an open frame is easy. I'll have to remember that if I ever have to pull it from below. I'm sure that it will be difficult.

The last thing to do before calling the transmission complete was to check the operation of the air shift for the auxiliary section. I dialed the shop air pressure down to 50 psi, hooked the supply up to the slave valve and attempted to shift - nothing, not even a hiss. The slave valve was frozen up. And to make matters even worse, the manufacturer, Parker, had used steel screws into the aluminum body to hold the cover on. After years in a corrosive environment, the screws and the body had chemically combined into one. So, the valve was headed for the recycle bin. When I received the new valve, I decided to tube it up instead of using hoses. Here it is installed:

It functions flawlessly - the auxiliary makes a nice clunk when I move the switch on the gear knob and shift through neutral. The transmission is now complete. One more thing to check off of the to-do list.

Time to start on the transmission rear support and cross member. It turns out that this is a multifaceted problem. It involves both the rear transmission support and the front drive shaft.

My first thought was to support the rear of the transmission from above. There is just enough clearance between the bottom of the cab and the top of the frame to sneak in a cross member. The support for the rear of the transmission would be tricky but doable.

Then I had a look at the front drive shaft. The truck is currently sitting about 1" above the bump stops (stock springs with a much heavier engine & transmission). This gives me a good idea of what will fit and what will not. Here's a look from the transfer case toward the front axle:

Here's a look in the opposite direction:

After some measuring, I concluded that the largest drive shaft that I could comfortably fit is 2" in diameter. The problem is that the distance from the center of the transfer case yoke to the center of the front axle yoke is 53". A 2" shaft that long is essentially a piece of spaghetti. A quick visit to Spicer's maximum RPM calculator confirmed this. Their calculated max RPM for a shaft with these dimensions is 2558. That will never do for a truck whose engine has a maximum governed RPM of 2800 and a transmission with a 0.80 to 1 overdrive. Conclusion - I need a center bearing for this shaft.

As an aside, I love Spicer. While some manufacturers act like data on their products are trade secrets, Spicer shares everything and provides helpful tools like the RPM calculator and torsional vibration analysis calculator.

That changed my transmission support design. Now I'm looking at supporting it from below. It's actually going to be a lot easier to connect to the transmission. It looks like Fuller intended that the rear support be from below. Here's my rear support mocked up in cardboard:

I purchased the parts to make the front drive shaft. Spicer has a data sheet that lists all the parts necessary for a 2 piece drive shaft. It's as simple as they could make it. Here are the parts:

I'm very happy with this transmission. It is robust and well built. I have overhauled a number of car and light truck transmissions. This is the first real truck transmission that I have worked on. The difference is dramatic - the other transmissions seemed designed to be assembled at the factory and never touched again. This transmission was obviously designed to be repaired. It was a joy to work on.